Low flow safety valve

ABSTRACT

A low flow safety valve according to the present invention relates to a valve construction that may be employed in conjunction with flow conduits such as well production tubing and the like. The valve construction is operative to allow the flow of production fluid through the valve structure as long as the rate of flowing pressurized fluid is above a predetermined minimum sufficient to develop a predetermined pressure differential across a restriction defined within the valve structure. As fluid flow and consequent pressure differential reduce below predetermined minimum levels, actuating means achieves closing of the valve and locking means effectively locks the valve structure against inadvertent reopening. The safety valve also includes means for unlocking and reopening the valve mechanism for the purpose of resuming production flow through the conduit structure with which the valve is associated.

United States Patent 3 [191 Kisling, III [451 Apr. 3,1973

[54] 1 LOW FLOW SAFETY VALVE Primary Examiner-Harold W. Weakley 75Inventor: James w; Kisling, III, Houston, Attorney-Arnold, White & BurkTex. [73] Assignee: Schlumberger Technology Corpora- [57] ABSTRACT tion,New York, NY.

Filed: Apr. 28, 1971 Appl. No.: 138,138

US. Cl. ..137/459, 137/465, 166/224 Int. Cl ..Fl6k 17/24 Field of Search..l37/458, 459, 460, 464, 465,

References Cited UNITED STATES PATENTS /1927 Blust ..l37/459 3/1917 Kail..l37/459 3/1964 Dickens ..l37/498 X A low flow safety valve accordingto the present invention relates to a valve construction thatmay beemployed in conjunction with flow conduits such as well productiontubing and the like. The valve construction is operative to allow theflow of production fluid through the valve structure as long as the rateof flowing pressurized fluid is above a predetermined minimum sufficientto develop a predetermined pressure differential across a restrictiondefined within the valve structure. As fluid flow and consequentpressure differential reduce below predetermined minimum levels,actuating means achieves closing of the valve and locking meanseffectively locks the valve structure against inadvertent reopening. Thesafety valve also includes means for unlocking and reopening the valvemechanism for the purpose of resuming production flow through theconduit structure with which the valve is associated.

Claims, 7 Drawing Figures PATENTEDACPRB I975 SHEET 1 [1F 3 IN VE N TORJames W. Kisling, HI

AMUM, Wide dmwlkee A TTORNEYS PATENTEDAPR 3 I975 SHEET 2 UF 3 Ja mes W.Kislingfll 4 IN VE N TOR A TTORNEYS LOW FLOW SAFETY VALVE FIELD OF THEINVENTION The present invention relates generally to safety valves andmore particularly to a safety valve mechanism that is operative .toallow the flow of production fluid above a predetermined volume at agiven pressure and to completely shut off the flow of production fluidwhen such flow decreases below the predetermined allowable rate.

BACKGROUND OF THE INVENTION In the early stages of development of thepetroleum industry it was typically the practice to tap a pressurizedsource or reservoir of petroleum products by drilling and to allow anygas pressure that might be contained therein to dissipate to acontrollable level or to a level at which the petroleum products mightbe recovered by pumping. The gas during this particular period wassubstantially unusable and was generally wasted. Where'oil was blownfrom the well along with the escaping gas, it was the practice tocollect the oil in surface ditches constructed about the well site. Asthe petroleum' industry rapidly developed, it was discovered that thepressurized gas within production formations could be efficientlyutilized to produce other petroleum products contained therein and thegas itself could be efficiently marketed in its natural state or inother physical states, such as the liquid state, for example. Variousdevelopments have been made to ensure against the loss of gas pressurewithin petroleum reservoirs, but most of the early developments wererelated to surface control valves and the like that might be manipulatedmanually or mechanically for flow control purposes.

Although wells may now be effectively controlled to prevent unnecessaryescape of gas from the reservoir, occasionally an unforeseencircumstance will develop that may cause a well to blow wild. Surfaceproduction control equipment may be damaged by mechanical apparatusoperating in the vicinity of the well site and the surface equipment ofthe well may be otherwise subject to various hazards of the surfaceenvironment that could result in blow-out of the well.

When the well is being produced through an offshore facility such as aproduction platform, the occurrence of an explosion or fire and the likeisextremely hazardous to lives of personnel because of the difficulty ofescape from the production facility. Offshore .explosions and fires arealso extremely expensive from a property damage standpoint because ofthe extremely expensive nature of offshore production facilities.Moreover, an oil spill that might be caused by damage to surfaceproduction flow controlequipment, located Wells may also blow-out due toshifting of earth stratum through which the well bore passes andlikewise, may blow-out due to insufficient structural interconnectionbetween well cement within the well flow around the exterior of the wellcasing to the surface.

When a well blows wild for any reason whatever, the expense thereof towell drilling and producing companies can be extremely great. Suchexpense, may be caused by loss of production during the time the well isblowing wild and due to the loss of field reservoir pressure which mayprevent future production of petroleum products in situ. Loss ofreservoir pressure may also substantially slow the production ofpetroleum products or may make the production of such products extremelyexpensive by requiring gas lifting operations and secondary recoveryoperations for effective production.

It is obviously necessary to provide subsurface production flow controlmechanisms that may be controllable automatically or selectively asdesired to prevent well blow-outs even though surface flow controlequipment may be damaged or rendered inopera-.

tive. Subsurface production flow control apparatus of this nature may becapable of preventing explosion and fires that otherwise might occur inthe event of damage or malfunction of surface flow control systems.Moreover, subsurface flow control safety equipment may effectivelyprevent the pollution of the surface environment that might otherwiseoccur if an offshore well is allowed to blow wild. Since subsurfacesafety valve mechanisms may effectively present a great majority of wellblow-outs and since pollution control is so extremely important from thestandpoint of conservation, it is obvious that subsurface safetymechanisms are necessary to efficient functioning of the petroleumindustry.

THE PRIOR ART Various well safety systems have been developed involvingboth surface and subsurface safety equipment that may be actuated to asafe position either automatically as by pilot mechanisms which may becontrolled by remote sensing or in the alternative may be actuatedselectively or automatically, in response to the development of anadverse well condition, to stop the flow of production fluid until theproduction equipment may be made safe for further operation.

Offshore wells may include production equipment provided with a safemode that may allow production or may shut-in the well in the event ofstorms or other hazardous conditions that might otherwise adverselyaffect production operations.

Surface and subsurface safety valve equipment ha been developed thateffectively achievesshut-in of surface or subsurface production flowcontrol equipment to terminate the flow of production fluid in the eventexcessive well pressures should develop and in the event the flowcontrol equipment. should be subjected to excessive flow of productionfluid. For the most part such safety valve equipment is velocitysensitive and remains open to allow the flow of production fluid duringperiods of normal or low flow of fluid but is actuated by forcesdeveloped by high velocity fluid to move the valve structure to theclosed position thereby terminating the flow of production fluid.

One hazard of virtually every type of safety valve systems is thatgenerally the valve seat and other valve closure structure is subjectedat all times to adverse well conditions, such as corrosion that might becaused by the well fluid and erosion that might be caused by sand andother foreign matter flowing along with the production fluid. If thesafety valve structure is eroded or corroded by flowing productionfluid, it may not be capable of functioning properly in the eventemergency conditions should subsequently develop.

Another adverse feature of presently available velocity sensitive safetyvalve mechanisms is that it is typically impossible or impractical toachieve testing of the safety mechanisms to ensure proper functioningthereof without necessitating removal of the valve structure from thewell. Also, it may be necessary to remove the string of productiontubing from the well which, of course, is an extremely expensive andundesirable operation.

Another problem that typically arises when velocity sensitive surface orsubsurface safety valve mechanisms are employed is the likelihoodthatthe velocity of flowing production fluid may not be sufficient toachieve effective shut-in ofthe well thereby allowing the well to blowunder low velocity conditions. This undesirable condition, of course, isaccentuated to an adverse degree if a condition of surface explosion orfire is involved. Velocity sensitive safety valves are capable ofclosing only after an adverse flow condition has developed, and whenclosure occurs, it takes the form of slamming the valve shut therebysubjecting the valve structure and other downhole well apparatus totremendous forces that could result in serious damage. It is typicallynecessary to provide velocity sensitive safety valve mechanisms withcontrol springs that, are specifically designed for the particularpressure and production flow conditions to which the productionequipment may be subjected. If the safety valve mechanism is allowed toremain for an extended period of time, production of the particularreservoir may reduce reservoir pressure and the consequent velocity offlowing production fluid to such a degree that the forces developedthereby may not be sufficient to achieve effective closing of thevelocity sensitive safety valve even when the well is allowed to flowinunrestricted manner. Also, if reservoir pressure should increase for anyparticular reason substantially above the pressure and flow velocityparameters for which the velocity sensitive safety valve mechanism hasbeen designed, the valve may permanently close thereby preventing anyproduction of petroleum products and thereby requiring the valve to bereplaced with a substitute valve that has been properly designed for theincreased reservoir pressure. Velocity sensitive safety valves areobviously ineffective when undulating or rapidly changing pressureconditions are encountered. Moreover, any change in reservoirenvironment that may occur, for example, due to encroachment of saltwater could produce adverse conditions that would interfere with properoperation of velocity sensitive safety valve mechanisms.

Accordingly, it is a primary object of the present .inv vention toprovide a novel safety valve mechanism capable of functioning properlyin a down-hole well environment to shut off the flow of production fluidin the event reservoir pressure and consequent volume of productionfluid should decrease below a predetermined minimum operating level.

It is another object of the present invention to provide a novel safetyvalve mechanism that is effective to close the production flow passagethrough the well tubing upon temporary cessation of the flow ofproduction fluid such as might be caused by closing of a surface valve.

An even further object of the present invention contemplates theprovision of a novel safety valve construction that is capable ofrendering surface flow control equipment safe for repair or servicingwithout subjecting repair or servicing personnel to hazardousconditions.

It is also an object of the present invention to provide a novel safetyvalve mechanism that may be simply and effectively tested to ensureproper operation thereof without necessitating expensive testingoperations such as the pulling of production tubing, the provision ofspecial testing equipment or removal of the safety valve from the tubingstring.

Among the several objects of the present invention is noted thecontemplation of a novel safety valve mechanism that may be reopened forfurther production of fluid through conduit structure with which it maybe associated after having been closed under emergency conditions simplyby increasing pressure within the production conduit downstream of thesafety valve mechanism to a pressure in excess of pressure upstreamthereof.

It is another feature of the present invention to provide a novel safetyvalve mechanism that may be implaced and removed by simple wire lineequipment thereby providing for simple and inexpensive servicing in theevent such should be indicated necessary by a testing procedure.

Still another feature of my invention includes the provision of a novelsafety valve construction for a down-hole well environment that may beemployed in tandem or in conjunction with velocity sensitive safetyvalve mechanisms to ensure complete safety control of the wellregardless of the type of adverse pressure conditions that might developeither at the surface or within the reservoir being produced.

Another object of my invention involves the provision of a novel safetyvalve mechanism that is capable of anticipating adverse flow conditionsand achieving closure without.

My invention also contemplates the provision of a.

novel safety valve mechanism that is of inexpensive nature and isreliable in .use in addition to being low in cost.

Other and further objects, advantages and features of the presentinvention will become apparentto one skilled in the art uponconsideration of the written specification; the attached claims and theannexed drawings. The form of the invention, which will now be describedin detail, illustrates the general principles of the invention, but itis to be. understood that this detailed description is not to be takenas limiting the scope of the presentinvention.

SUMMARY OF THE INVENTION A preferred embodiment of the present inventionmay comprise an elongated generally tubular housing within which ismovable disposed a sleeve member having a production passage definedtherein. A valve element, which may be a spherical plug valve, ifdesired, is carried by the sleeve member and includes a valve passagethat is communicated with the production passage in the open position ofthe valve to allow the flow of production fluid through the productionpassage. The valve housing may includes means, cooperating with thevalve element, to achieve move ment thereof between open" and closedpositions, responsive to movement of the sleeve member within thehousing. The sleeve member may be biased in a direction tending toachieve closure of the valve element by a compression spring or by anyother suita'ble biasing means interposed between the sleeve member andthe housing structure. A restriction means such as a choke may bedisposed within the sleeve structure and is effective to achievedevelopment of a differential pressure within the sleeve structure thatcreates a force of sufficient magnitude, acting upon the sleevestructure and opposing the biasing means, to overcome the biasing meansand maintain the valve element in the open position as long as the flowof production fluid is above a predetermined minimum volume. In theevent such flow of production fluid should decrease below the minimumoperating volume, the biasing means will overcome the force ofproduction fluid acting upon the sleeve member and induce movement ofthe valve element to the closed position thereof, thereby ceasingfurther flow of production fluid.

Detent means may be provided by the valve housingand sleeve to achievelocking of the sleeve member in the position achieving closure of thevalve element thereby effectively preventing reopening of the valveelement after automatic closure thereof has been achieved. Means mayalso be provided to unlock the detent mechanism, responsive to selectiveinjection of pressure downstream of the valve element, to substantiallybalance downstream of the valve element. Such unlocking means mayconveniently take the form of a pressure actuated piston having anunlocking cam thereof that disengages the detent mechanism and allowsthe biasing means to move the sleeve element to a position causingcooperating structure between the valve element and housing to inducemovement of the valve element to the open position thereof.

BRIEF DESCRIPTION OF THE DRAWINGS It is to be noted, however, that theappended.

drawings illustrate only a typical embodiment of the invention and are,therefore, not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

In the drawings:

FIG. 1 is a pictorial representation, illustrated partially in section,of a subsurface earth formation having a well bore extended therethroughand being lined with a well casing enclosing a production tubingcontaining a down-hole safety valve mechanism constructed in accordancewith the present invention.

FIG. 2 is a fragmentary sectional view of the well cas ing structure ofFIG. 1 illustrating a typical landing nipple and showing wire-lineimplacement and retrieval apparatus having a safety valve mechanism,constructed according to this invention, connected to the lowerextremity thereof.

FIG. 3 is a sectional view of the low flow safety valve mechanism ofthis invention illustrating the moving parts in the normal fluidproducing position thereof.

FIG. 4 is a sectional view of the safety valve structure of FIG. 3 withthe internal moving parts depicted in the closed position thereof.

FIG. 5 is a fragmentary sectional view of thesafety valve mechanism ofFIGS. 3 and 4 illustrating the unlocking mechanism in the positionthereof achieving unlocking of the latching detent mechanism.

FIG. 6 is a fragmentary sectional view of the upper portion of thesafety valve mechanism of FIGS. 3 and 4, illustrating the detentunlocking mechanism in greater detail.

FIG. 7 is a fragmentary sectional view of the lower portion of thesafety mechanism of FIGS. 3 and 4 illustrating the valve and chokemechanism ingreater detail.

DESCRIPTION OF PREFERRED EMBODIMENT Now referring to the drawings andfirst to FIG. 1, an earth formation is illustrated at 10 having awellbore 12 drilled therein which is lined with a well conduit 14 that maybe cemented in place in conventional manner. Productiontubing 16,typically referred to in the industry as a tubing string, extendsthrough the well casing 14 and is sealed with respect to the well casingby a packer 18 located a convenient distance above the production zoneof the earth formation. The tubular conduit 16 is open at its lowerextremity to production fluid flowing through perforations in the casing14 and conducts the production fluid upwardly through the tubing stringin conventional manner.

For the purpose of shutting off the flow of production fluid through thetubing 16 in the event production flow in the tubing should decreaseabnormally, it will be desirable to provide a safety valve mechanismthat is responsive to predetermined decrease in the flow of productionfluid to close and effectively shut off the flow of fluid. According tothe present invention, such safety valve mechanism may conveniently takethe form illustrated in the drawings where a safety valve mechanism isdepicted generallyat 20 that may be installed and removed byconventional wire-line equipment, illustrated generally at 22. It willbe convenient to install the safety valve within the tubing string at alevel where the temperature is high enough to prevent solidification ofparaffin which might otherwise cause fouling of the movable valve parts.

With reference now to FIG. 2, the wire-line apparatus 22 is shown toinclude a landing nipple 24 that may be provided with externallythreaded extensions 25 and 26 that receive internally threadedextremities of the production tubing 16. An annular landing shoulder 28may be defined within the lower extension 26 of landing nipple 24 forengagement by an annular shoulder 30 formed on a wire-line tool 32thereby preventing the wire-line tool from descending below the levelestablished by annular shoulder 28. Wire-line tool 32 may be providedwith locking detents 34 adapted to be received within an annular lockinggroove 36 defined within landing nipple 24.. Wire-line tool 32 may alsobe provided with a packing 38 of annular configuration for engagementwith the cylindrical surface 40, defining a portion of the receptaclefor the wire-line tool. As is typically the case, wire-line tool 32 mayalso be provided with a fishing neck 42 at the upper extremity thereofthat may be engaged by appropriate installation and retrieval apparatusof conventional nature.

While the particular wire-line installation and retrieval apparatus 32is illustrated in FIG. 2, it is to be understood that the particularconfiguration illustrated is not intended to limit the presentinvention. It is intended to be obvious that any suitable wire-line toolof conventional nature may be employed within the spirit and scope ofthe present invention. The wireline tool 32 may be provided with a lowerexternally threaded extremity 44 adapted for threaded connection tointernal threads 46 formed within the upper extremity of an upperhousing section 48 of the safety valve mechanism 20, thereby effectivelysupporting the safety valve in depending relation from the wire-linetool 32.

The safety valve mechanism may include a housing structure defined byupper housing section 48, latching section 50, spring housing section52, valve section 54 and a terminal cap section 56. Latching section 50may be provided with externally threaded portions 58 and 60 forthreaded'engagement with the internally threaded portion 62 of upperhousing section 48 and the internally threaded portion 64 of the springhousing section 52. Spring housing section 52 may be provided with anexternally threaded extension 66 at the lower extremity thereof to whichmay be threadedly engaged the internally threaded portion '68 of thevalve section 54. Terminal cap section 56 may be provided with anexternally threaded extension 70 that may be threadedly received byinternal threads 72 defined within the lower extremity of valve section54.

The valve mechanism 20 may be provided with an internal sleeve 74, thelower extremity of which is shown in detail in FIG. 7, which may beprovided with a reduced diameter portion 76 defining an annular shoulder78 adapted for engagement by a compression spring'member 80 that isdisposed within spring housing section 52 and interposed betweenshoulder 78 and an upper annular shoulder 82 defined by the lowerextremity of latching section 50. Compression spring 80 is operative tobias the sleeve member 74 downwardly, as illustrated in the drawings.Although compression spring 80 is illustrated as a metal helical spring,it is intended that any appropriate biasing means may be incorporatedinto the valve structure to achieve biasing of the sleeve member 74downwardly in a direction opposing the flow of production fluid withoutdeparting from the spirit and scope of the present invention. It is tobe understood that the mechanism for imparting movement of the valveelement to the closed position thereof may take any desirable form otherthan a biasing means. For example, a servo mechanism may achieve closureof the valve element responsive to sensing the predetermined flowcondition necessary for closure of the safety valve. A productionpassage 84 may be defined within the sleeve 74 and serves to conduct theflow of production fluid through the valve structure.

The lower extremity of sleeve 74 may be provided with external threads86, as illustrated in FIG. 7, to which may be threadedly connected theinternally threaded portion 88 of a valve and choke support element 90.The lower extremity of sleeve 74 may also be provided with an enlargeddiameter choke recess defined by a generally cylindrical bore 92 withinwhich is received a choke member 94 having a restricted flow passage 96formed therethrough. Annular shoulders 98 and 100 defined, respectively,within sleeve 74 and the valve and choke support element 90, cooperateto retain the choke member 94 in substantially fixed relation relativeto the sleeve structure. Annular sealing means 102 may be provided toestablish sealed relation between cylindrical surface 92 and sleevemember 74 which, according to the present invention, if desired, maytake the form of an O-ring, as illustrated, or, in the alternative, thesealing element 102 may take any other appropriate conventionalconfiguration within the spirit and scope of the present invention.

The valve and choke support element 90 may be provided with an annulargroove 104 within which is retained valve support elements, illustratedin broken line at 106, having support extensions 108 defined thereon towhich may be connected the trunnions 110 of a rotatable spherical plugmember 112. The plug member or valve element may be provided with aninternal valve passage 114 that is adapted, in the open position of thevalve element, to communicate with a flow passage 116 defined within thesupport element 90. Support element 90 may also be provided with anannular seat surface 118 disposed for engagement with a sphericalworking surface 120 on the plug or valve element 112. It is intendedthat the valve element 112 may take any other appropriate form otherthan the spherical form within the spirit and scope of this invention-For the purpose of imparting rotatable movement to valve element 112between the open and closed positions thereof, a cam groove may beformed in the valve element, as illustrated in broken line at 122,within which may be received a cam .element 124 in the form of a pincarried in fixed relation by the valve section 54 of the valve housing.As the valve element is moved downwardly by the sleeve 74 and valve andchoke support element 90 in the direction opposing the flow ofproduction fluid, the interengaged relation between cam element 124 andthe cam groove 122 will be operative to effect 90 rotation of valveelement 112 from the open position thereof, as illustrated in FIGS. 3and 7, to the closed position thereof, as illustrated in FIG. 4.

Since the flow of production fluid through the valve passage 114 may bequite high, it may be appropriate to provide a means for stabilizing thevalve element against shattering forces or vibration that might becreated by fluid turbulence and also a means may be provided to directthe flow of fluid smoothly through the valve passage 114. According tothe present invention, such stabilizing means may conveniently take theform illustrated in detail in FIG. 7 where a valve stabilizer 126 isshown to be movably disposed within the valve section portion 54 of thevalve housing and is provided with a seat surface 128 disposed forengagement with the spherical working surface 120 of valve element 112.A biasing means 130 which, if desired, may take the form of a metallichelical compression spring, may be interposed between a shoulder 132defined on the valve stabilizer 126 and an annular shoulder 134 definedby the upper extremity of terminal cap section 56 of the valve housingstructure. The compression spring 130 is operative to bias the valvestabilizer 126 into engagement with the valve element 112, therebyserving to firmly encapsulate the valve element between sealing surfaces128 and 118 to enhance the sealing ability of the valve element and toprevent vibration of the valve element by fluid turbulence. The valvestabilizer 126 may also be provided with an extension 136 defining anexternal guide surface 138 that serves to maintain-positive alignment ofthe valve stabilizer in any particular position thereof and to allowmovement of the valve stabilizer as the valve element is reciprocatedduring opening and closing movements thereof. V

A wiping ring 140 may be received within an annular groove 142 formed inthe terminal cap section 56 and may be disposed for close fittingrelation with the cylindrical surface 138 of the valve stabilizer 126 toprevent foreign matter, that might be contained within the flowingproduction fluid, from entering the annulus defined between the valvehousing and the internal movable parts of the safety valve. The wiperelement 140 is not provided for the purpose of establishing afluid-tightseal,-because it is desirable, as will be explained in detailhereinbelow, that fluid pressure be communicated into the annulus forvalve control purposes. Fluid communication, from the terminal capportion 56 of the valve housing to the valve element, may beconveniently provided by fluid passage 144 defined within valvestabilizer 126 that may be appropriately disposed coextensive with valvepassage 114 in the open position of the valve element. 7

With reference now particularly to FIG. 6, a means may be provided forthe purpose of locking thejsleeve element 74 in the downward positionthereof subsequent to actuation of valve element 112 to its closedposition and, according to the present invention, such means mayconveniently take the form illustrated in FIG. 6 where the sleeve 74 isshown to be provided with an annular locking groove 146 defining anannular shoulder 148. The latching section 50 of the housing structuremay include a plurality of latching fingers 150, each being providedwith latching detents 152 capable of being received within the latchinggroove 146 upon movement of sleeve element 74 to the lowermost positionthereof. Latching fingers 150 may be spring biased toward such latchingengagement to cause locking shoulders 154 of the detents 152 to engagethe annular shoulder 148 to restrain or lock the sleeve member 74 in thedownward position thereof. It

.is also within the scope of this invention to provide desiredto openthe valve. A servo mechanism or any other appropriate system may beemployed to open the valve selectively or automatically upon restorationof the safe operating condition.

After the sleeve 74 has moved downwardly to close the valve element 112and the detents 152 have moved into locking engagement within thelatching gr'oove 146, subsequent pressure change upstreamof valveelement 112 will not be effective to achieve reopening of the valveelement. After automatic emergency locking of the sleeve 74 in the valveclosing position thereof, it will subsequently become appropriate tounlock the sleeve when it is desired to achieve movement of the valveelement to the open position thereof to resume the flow of productionfluid. An unlocking means is provided, which, according to the presentinvention, may conveniently take the form illustrated in FIG. 6 whereinan annular unlocking piston 156 may be movably disposed within anannular chamber 158 defined between an inner wall 160 of upper housingsection 48 and an external cylindrical surface 162 defining the upperextremity of sleeve 74 above locking groove 146. Unlockingpiston 156 maybe provided with an internal sealing element 164 and an external sealing166 to maintain sealing relation between the unlocking piston and thecylindrical surfaces 162 and 160, respectively.

For the purpose of releasing the latched connection between detentmembers 152 and the annular shoulder 148, defined by latching groove146, an unlatching'extension 168 maybe formed integrally with unlockingpiston 156 and may be provided with a cam surface 170 disposed forengagement with opposed cam surfaces 172, defined at the upper extremityat each of the latching fingers 150. As unlocking piston 156 is moveddownwardly, cam surface 170 will move into engagement with cam surfaces172 and will actuate the spring fingers outwardly, thereby causingdisengagement of the locking shoulders 154 of the spring fingers fromthe annular shoulder 148 defined on the sleeve 74. After this unlockingmovement has occurred, the sleeve 74 will have. been released and willbe capable of being moved upwardly to impart rotation to valve element112 to the open position thereof to resume the flow of production fluidthrough the valve structure.

Unlocking piston156 may be designed for movement by fluid pressure thatmay be applied either by the production fluid or by an actuating fluidapplied under pressure from a source located downstream of the safetyvalve structure. While the valve 112 is disposed in the production modethereof as illustrated in FIG. 7, production fluid under pressure willmaintain the unlocking piston 156 at the upper limit of its travel wherefurther upward movement thereof is prevented by a stop shoulder 174.

OPERATION Assuming the safety valve mechanism of the present inventionto be disposed in the open position thereof, as illustrated in FIGS. 3,6 and 7, it will be apparent that production fluid will flow from thewell casing into the open lower extremity of the safety valve mechanism20 under reservoir pressure. Since valve element 112 will be maintainedin its open position. in the production mode, fluid pressure will becommunicated through the valve passage 114, the flow passage 116 andthrough the restricted passage 96 of choke 94 into production flowpassage 84.

As the pressurized production fluid passes through the restrictedorifice defined by choke passage 96, a pressure differential will becreated across the choke thereby producing a force acting upon thesleeve 74 in a direction opposing the bias of compression spring 80. Theforce acting through sleeve 74 will be sufficient during normalproduction flow to overcome the bias of compression spring 80 andmaintain the sleeve member 74 at the uppermost position thereof where anannular shoulder 176 of the valve and choke support element 90 isdisposed in restraining engagement with a stop surface 178 defined bythe lower extremity of spring housing section 52 of the valve housing.

The annulus between the valve housing wall and the internal movableparts of the safety valve structure will be subjected to reservoirpressure passing the wiping ring 140 which acts upon the lower surfacearea defined by the annular unlocking piston 156. Since a reducedpressure will be acting upon the surface area defined by the upperextremity of the unlocking piston 156 by virtue of the choke reduction,the fluid pres sures acting upon the piston 156 will be unbalancedthereby creating a resultant force biasing the piston upwardly intoengagement with the stop surface 174. The valve and choke supportelement 90, along with valve element 112, will be moved to theiruppermost positions by sleeve 74 and the valve stabilizer 126 will bebiased by spring 130 to its uppermost position maintaining a stabilizingbias upon the spherical valve element 112.

In the event the flow of production fluid should decrease for anyreason-whatever, such as by reduction in reservoir pressure, bytemporary closing of surface production control valves or by thecreation within the production tubing of a pressure approaching thereservoir pressure, the resultant force acting upon sleeve 74, createdby the pressure differential across choke 94, will be insufficient toovercome the bias of compression spring 80. The compression spring thenwill urge the sleeve element 74 downwardly thereby moving the valve andchoke support element 90 and consequently the spherical plug valveelement 112 downwardly and causing thecam pin 124 acting through camgroove 122 to actuate the valve element to the closed position thereof,as illustrated in FIG. 4. Downward movement of the sleeve and valveassembly is limited under this condition by an annular stop shoulder 178defined on the valve stabilizer 126 that is adapted for engagement withshoulder surface 134.

If in the valve closed position of the safety valve, as shown in FIG. 3,the casing below the safety valve should remain under reservoir pressureeven under a reduced pressure condition, such fluid pressure will actthrough the annulus defined between the valve housing wall structure andthe internal moving parts of the valve-structure and will bear upon thelower surface area defined by the annular unlocking piston 156, therebymaintaining the unlocking piston at the uppermost position thereof, asillustrated in FIG. 6.

If the production pressure conditions should resume a normal level,subsequent to closing of the spherical plug 112, the valve constructionwill remain in a closed position because of the latching engagementbetween the detents 152 of spring fingers 150 which will maintainengagement with the annular shoulder 148 of sleeve 74, therebypresenting the sleeve member from again moving upwardly which wouldobviously allow opening of the valve element.

The safety valve construction may be opened by selective application ofactuating fluid pressure above the valve 112 at a pressure levelinexcess of reservoir pressure. Such actuating fluid pressure iseffective to develop a resultant force, acting upon the upper surfacearea defined by annular unlocking piston 156, that is greater than theforce created by reservoir pressure acting upon the lower surface areaof piston 156. The piston therefore will be induced to move downwardlycausing the cam surface 170 of the unlocking extension 168 to engage camsurfaces 172 of the spring fingers 150 thereby urging the spring fingersoutwardly and releasing shoulders 154 of locking detents 152 from theannular shoulder 148 of the sleeve element. After the spring fingershave been unlatched from the sleeve element there will exist asubstantially balanced pressure condition within the valve structure dueto substantial balancing between reservoir pressure and the actuatingpressure injected into the tubing above the valve element to cause theunlocking movement. Compression spring 80, under this condition, willcontinue to maintain the sleeve element biaseddownwardly, therebymaintaining the spherical plug 112 in a closed position thereof.

It will then be necessary to reduce fluid pressure above the valveelement simply by bleeding off the same by appropriate manipulation ofsurface flow control valves, thereby causing reservoir pressure tooverbalance actuation pressure above the safety valve. When sufficientpressure differential occurs across the choke to produce a force, actingon the sleeve, that is sufficient to overcome the bias of compressionspring,

80, the plug member, the valve and choke support element and the sleeveelement 74 will be forced upwardly and will thereby cause the plugmember 112 to be rotated to the open position thereof by virtue of theinterengagement between cam pin 124 and plu'g groove 122. This movementcan take place slowly thereby preventing any slamming of the valve partswhich might otherwise cause damage to the valve. During the openingmovement the unlocking extension 168 maintains its engagement withspring fingers until sufficient' resultant force is developed to causethe unlocking extension to cam the spring fingers outwardly to achievereleasing thereof. This feature eliminates the'possibility of relockingof the sleeve which might otherwise occur if the piston were free tomove upwardly upon application of insignificant pressure differential.After plug member 112 has been fully opened and full production flow hasbeen resumed, the valve construction will remain static until such timeas the flow of pressurized fluid is again reduced to the predeterminedminimum level necessary for automatic actuation of the valve-to itsclosed position.

Assuming that the reservoir pressure remains at an optimum level, but itis deemed appropriate to conduct a test to determine whether the valveconstruction is operative, it will simply be necessary to manipulatesurface flow control equipment to reduce the flow of production fluidthrough the safety valve below the predetermined minimum volume.required for automatic actuation of the safety valve. If the valveconstruction is operative, the compression spring 80 will bias sleeveelement 74 downwardly inducing closing of the plug member 112 in themanner discussed hereinabove. Subsequent to the completion of asuccessful test the safety valve may again be reopened to resume theflow of production fluid by injection of fluid pressure into the tubingabove the safety valve in the manner discussed hereinabove. The testingprocedure is simple, reliable and quite inexpensive. It becomesnecessary to remove the safety valve from the well for repair orreplacement only when it is determined, through the testing procedureindicated above, that the valve construction is in need of repair orreplacement. Moreover, replacement or repair procedures are readily andinexpensively accomplished because it is unnecessary to'remove thetubing string from the well. The wire-line tool 32 maybe unlocked andretrieved in conventional manner along with the safety valve attachedthereto, and subsequent to the valve repair or replacement procedure,may be reinstalled within the well in simple conventional manner.

It will be evident from the foregoing that I have provided anovel safetyvalve mechanism that iscapable of functioning properlyin a down-holewell environment to shut off the flow of production fluid in the eventthat flow of production fluid should decrease for any reason whateverbelow a predetermined operative level. The safety valve mechanism of myinvention also effectively achieves closing of the production flowpassage through the well tubing upon temporary cessation of the flow ofproduction fluid such as might be caused by closingof a surface valve orby creation within the production tubing of a back pressure sufficientto at least temporarily reduce the flow of production fluid below thepredetermined minimum operating level. I have also achieved theprovision of a novel safety valve mechanism that may be simply andeffectively tested to ensure proper operation thereof at all timeswithout necessitating an expensive testing operation and withoutrequiring removal of the production tubing from the well. Also with theflow of production fluid shut down by simple valve closure the flow ofproduction fluid may be restrained solely by the safety valve mechanismwhile the surface flow control mechanism may be serviced or repairedwithout subjecting personnel to hazardous conditions.

After an emergency shut down, a testing procedure or a procedureinvolving repair of surface flow control equipment, the safety valvemechanism of my invention may be reopened simply by applying fluidpressure within the production tubing above the safety valve in themanner discussed hereinabove. Such reopening can be achieved effectivelywithout involving slamming of the valve parts which might otherwiseoccur upon sudden subjection of the valve structure to reservoirpressure. The safety valve mechanism of my invention is adapted forsimple connection to a conventional wire line tool thereby allowing thesafety valve to be in place and retrieved by conventional wire lineproduction tool apparatus. This feature effectively eliminates anynecessity for removing the tubing string if it is determined that thesafety valve shouldbe cleaned, repaired or replaced; Moreover, thesafety valve mechanism of my invention can be effectively employed in adown hole well environment in tandem or in conjunction with aconventional velocity sensitive safety valve mechanism, if desired,thereby lending safety valve capability under virtually all possiblepressure and flow conditions that might develop either at the surface orwithinthe reservoir being produced lt is therefore seen that thisinvention is one well adapted to attain all of the objects andadvantages hereinabove set forth together with other advantageswhichwill become obviou's and inherent from a description of the apparatusitself. It will be understood that certain combinations andsubcombinations are of utility and may be em ployed without reference toother features'and subcombinations. This is contemplated by and iswithin the scope of the present invention.

As many possible embodiments may be made of this invention withoutdeparting from the spirit or scope thereof, it is to be understood thatall matters hereinabove setforth or shown in the accompanying drawingsare to be interpreted as illustrative and not any limiting sense.

What is claimed is:

1. A safety valve assembly comprising:

housing means;

valve means disposed within said housing means and being'movable betweenopen and closed positions to control the flow of production fluidthrough said valve assembly;

means urging said valvemeans toward the closed position thereof; 7

means responsive to predetermined rate of flow of production fluid.through said valve assembly for maintaining said valve means in the openposition thereof; e

means closing said valve means upon decrease in the flow of productionfluid below said predetermined rate of flow;

means locking said valve means against reopening after closure thereofby said urging means; and

means. releasing said valve means from the locked condition thereof inresponse to application of predetermined fluid pressure downstream ofsaid valve means.

2. A safety valve assembly as recited in claim 1:

valve sleeve means movably disposed within said housing means and.defining a flow passage through said safetyvalve assembly;

said valve means being movably supported by said sleeve means and havinga flow port for registry with said flow passage in the open position ofsaid valve means; v v

said means biasing said. valve means toward the closed position thereofbeing resilient meansintenposed between said housing and said sleevemeans;

said means for maintaining said valve in the open position thereofcomprising flow passage means formed in said sleeve means for conductingthe flow of production fluid therethrough; and

means restricting said flow passage and causing fluid flowing throughsaid flow passage to develop a pressure differential within said flowpassage across said restricting means and thereby develop a resultantforce acting on said sleeve means and opposing said biasing means, saidresultant force being effective to overcome said biasing means andmaintain said sleeve means at a position causing said valve means to bemaintained in the open position thereof in response to a predeterminedrate of flow through said flow passage.

3. A safety valve assembly as recited in claim 1:

sleeve means being disposed for reciprocation within said housing meansand having flow passage means defined therethrough; and I said valvemeans being a spherical plug valve rotatably carried by said sleevemeans and having a flow port formed therein for registry with said flowpassage of said sleeve means, said valve means being rotatable betweenopen and closed positions thereof responsive to reciprocation of saidsleeve means.

4. A safety valve assembly as recited in claim 1:

sleeve means disposed for reciprocal movement within said housing meanshaving a production flow passage defined therein; 7

said valve means being movably carried by said sleeve means and beingmovable between open and closed positions thereof responsive toreciprocal movement of said sleeve means to control the flow ofproduction fluid through said production flow passage;

said means locking said valve means comprising latch means carried bysaid housing;

latch detent means defined in said sleeve; and

said latch means and detent means interengaging to lock said sleeveagainst movement upon movement of said sleeve to a position causingclosure of said valve means by said biasing means in response topredetermined decrease in differential pressure within said valveassembly.

5. A safety valve assembly comprising:

elongated tubular housing means being open at each extremity thereof;

sleeve means being movably disposed within said housing and having aproduction passage formed therein;

means urging said sleeve means toward one extremity of said housing;

valve means being carried by said sleeve means and being movable betweenopen nd closed positions thereof to control the flow of production fluidthrough said production passage;

said urging means urging said valve means toward said closed position;

means responsive to predetermined flow of production fluid through saidproduction passage for urging said sleeve means against the bias of saidvalve means locking said sleeve means against movement upon closure ofsaid valve means; and

means releasing said sleeve from the locked condition thereof inresponse to application of predetermined fluid pressure downstream ofsaid valve means.

6. A safety valve as recited in claim 5:

means defining a restriction within said production passageand v theflow of pressurized production fluid through said restriction developinga pressure differential across said restriction and developing aresultant force acting on said sleeve means and opposing the force ofsaid urging means.

7. A safety valve as recited in claim 5:

said means for urging said sleeve means against the force of said urgingmeans defining a restriction within said production passage;

the flow of a predetermined volume of pressurized production fluidthrough said restriction developing a pressure differential across saidrestriction and developing a resultant force overcoming said urgingmeans and maintaining said valve means in the open position thereof;

said means locking said valve element in the closed position thereofupon closure of said valve element including latch means carried by saidhousing;

latch detent means being defined in said sleeve means; and

said latch means and detent means interengaging to lock said sleeveagainst movement upon movement of said sleeve to a position causingclosure of said valve means by said biasing means in response topredetermined decrease in differential pressure within said valveassembly.

8. A safety valve as recited in claim 7:

means for selectively unlocking said valve element and allowing openingthereof.

9. A safety valve as recited in claim 5:

said means locking said valve element comprising a latching groovedefined in said sleeve means;

a plurality of spring fingers carried by said housing and having detentmeans defined thereon for locking engagement within said latching grooveupon movement of said sleeve to a position closing said valve means; and

means for selectively disengaging said spring fingers from said latchinggroove.

10. A safety valve as recited in claim 9:

said means for selectively disengaging said spring flngers comprisingpiston means having unlatching cam means disposed thereon; and

said piston being movable to the unlatching position thereof responsiveto application of fluid pressure downstream of said valve and beingmovable to a retracted position by pressure of said production fluid.

1. A safety valve assembly comprising: housing means; valve meansdisposed within said housing means and being movable between open andclosed positions to control the flow of production fluid through saidvalve assembly; means urging said valve means toward the closed positionthereof; means responsive to predetermined rate of flow of productionfluid through said valve assembly for maintaining said valve means inthe open position thereof; means closing said valve means upon decreasein the flow of production fluid below said predetermined rate of flow;means locking said valve means against reopening after closure thereofby said urging means; and means releasing said valve means from thelocked condition thereof in response to application of predeterminedfluid pressure downstream of said valve means.
 2. A safety valveassembly as recited in claim 1: valve sleeve means movably disposedwithin said housing means and defining a flow passage through saidsafety valve assembly; said valve means being movably supported by saidsleeve means and having a flow port for registry with said flow passagein the open position of said valve means; said means biasing said valvemeans toward the closed position thereof being resilient meansinterposed between said housing and said sleeve means; said means formaintaining said valve in the open position thereof comprising flowpassage means formed in said sleeve means for conducting the flow ofproduction fluid therethrough; and means restricting said flow passageand causing fluid flowing through said flow passage to develop apressure differential within said flow passage across said restrictingmeans and thereby develop a resultant force acting on said sleeve meansand opposing said biasing means, said resultant force being effective toovercome said biasing means and maintain said sleeve means at a positioncausing said valve means to be maintained in the open position thereofin response to a predetermined rate of flow through said flow passage.3. A safety valve assembly as recited in claim 1: sleeve means beingdisposed for reciprocation within said housing means and having flowpassage means defined therethrough; and said valve means being aspherical plug valve rotatably carried by said sleeve means and having aflow port formed therein for registry with said flow passage of saidsleeve means, said valve means being rotatable between open and closedpositions thereof responsive to reciprocation of said Sleeve means.
 4. Asafety valve assembly as recited in claim 1: sleeve means disposed forreciprocal movement within said housing means having a production flowpassage defined therein; said valve means being movably carried by saidsleeve means and being movable between open and closed positions thereofresponsive to reciprocal movement of said sleeve means to control theflow of production fluid through said production flow passage; saidmeans locking said valve means comprising latch means carried by saidhousing; latch detent means defined in said sleeve; and said latch meansand detent means interengaging to lock said sleeve against movement uponmovement of said sleeve to a position causing closure of said valvemeans by said biasing means in response to predetermined decrease indifferential pressure within said valve assembly.
 5. A safety valveassembly comprising: elongated tubular housing means being open at eachextremity thereof; sleeve means being movably disposed within saidhousing and having a production passage formed therein; means urgingsaid sleeve means toward one extremity of said housing; valve meansbeing carried by said sleeve means and being movable between open ndclosed positions thereof to control the flow of production fluid throughsaid production passage; said urging means urging said valve meanstoward said closed position; means responsive to predetermined flow ofproduction fluid through said production passage for urging said sleevemeans against the bias of said valve means in the open position thereof;said urging means closing said valve means upon reduction of the flow ofproduction fluid below said predetermined flow; means locking saidsleeve means against movement upon closure of said valve means; andmeans releasing said sleeve from the locked condition thereof inresponse to application of predetermined fluid pressure downstream ofsaid valve means.
 6. A safety valve as recited in claim 5: meansdefining a restriction within said production passage; and the flow ofpressurized production fluid through said restriction developing apressure differential across said restriction and developing a resultantforce acting on said sleeve means and opposing the force of said urgingmeans.
 7. A safety valve as recited in claim 5: said means for urgingsaid sleeve means against the force of said urging means defining arestriction within said production passage; the flow of a predeterminedvolume of pressurized production fluid through said restrictiondeveloping a pressure differential across said restriction anddeveloping a resultant force overcoming said urging means andmaintaining said valve means in the open position thereof; said meanslocking said valve element in the closed position thereof upon closureof said valve element including latch means carried by said housing;latch detent means being defined in said sleeve means; and said latchmeans and detent means interengaging to lock said sleeve againstmovement upon movement of said sleeve to a position causing closure ofsaid valve means by said biasing means in response to predetermineddecrease in differential pressure within said valve assembly.
 8. Asafety valve as recited in claim 7: means for selectively unlocking saidvalve element and allowing opening thereof.
 9. A safety valve as recitedin claim 5: said means locking said valve element comprising a latchinggroove defined in said sleeve means; a plurality of spring fingerscarried by said housing and having detent means defined thereon forlocking engagement within said latching groove upon movement of saidsleeve to a position closing said valve means; and means for selectivelydisengaging said spring fingers from said latching groove.
 10. A safetyvalve as recited in claim 9: said means for selectively disengaging saidspring fingers comprising piston means havinG unlatching cam meansdisposed thereon; and said piston being movable to the unlatchingposition thereof responsive to application of fluid pressure downstreamof said valve and being movable to a retracted position by pressure ofsaid production fluid.